US 3744527 A
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United States Patent 1 Mercier 1 3,744,527 [4 1 July 10,1973
1 1 PULSE DAMPER UNIT FOR HYDRAULIC SYSTEM  Inventor: Jacques H. Mercier, 49 rue de Naples, Paris, France  Filed: July 13, 1972  Appl. No.: 271,602
 Foreign Application Priority Data Primary Examiner-Samuel B. Rothberg Assistant Examiner-Steven M. Pollard Attorney-Arthur B. Colvin  ABSTRACT The present invention relates to a pulse damper unit for a hydraulic system and comprises a rigid container with two opposed ports, each having an associated tubular fitting defining an inlet and outlet respectively for connection of the unit to the hydraulic system. A flexible separator in the form of a bladder having two opposed ports, is positioned in the container defining an inner and outer chamber with said bladder ports being associated with and operatively connected to said fittings. A tube'extending axially in said container, has its ends operatively connected to said tubular fittings, one end of said tube being rigidly secured to an associated fitting and the other end of the tube being slidably mounted with respect to an associated fitting. The tube defines a longitudinal passageway connecting said tubular fittings and has a permeable wall providing communication between said passageway and said inner chamber, a baffle adjustably mounted in said tube insuring that all of the hydraulic fluid entering the inlet fitting will flow through said permeable wall into said inner chamber before discharge from said outlet fitting. A third fitting is connected to a port leading into said container and in communication with said outer chamber, for charging of said outer chamber with fluid under pressure in order to dampen pulses in the hydraulic system.
. 11 Claims, 3 Drawing Figures PATENIEU JUL 1 0 ma sumzorz 1 PULSE DAMPER UNIT FOR HYDRAULIC SYSTEM As conducive'to an understanding of the invention, it is noted that due to the action, for example, of the pump used in a hydraulic system, pulses are developed which may be of relatively high frequency and amplitude. Such pulses may cause damage to the components of the system, such as by causing bursting of the hydraulic lines, and damage to valves and fittings, with resultant malfunctiong of the system.
The problem is enhanced when under certain operating conditions harmonics may develop with resultant increase in the pulse frequency and amplitude.
Where a unit is used in which the hydraulic liquid passes through an axial perforated tube rigidly secured in a container and encompassed by a deformable bladder, which defines a gas chamber with respect to the container, and a liquid chamber with respect to the tube, if the perforations in the tube are large enough to permit sufficient flow for effective dampening action, extrusion of the bladder may occur with resultant malfunctioning of the system.
Furthermore, if the tube is rigidly secured at both ends, expansion and contraction of the tube may cause cracking thereof also with resultant malfunctioning of the system.
Where substantially all of the liquid entering the unit is not subjected to the dampening effect thereof, the unit will be inefficient in operation, for pulses at a relatively high frequency, i.e., above 60 Hz.
It is accordingly among the objects of the invention to provide a pulse damper unit which may readily be fabricated at relatively low cost and may readily be assembled and disassembled for maintenance and repair, which unit will insure that all of the liquid entering the inlet thereof will be subjected to the dampening effect thereof before discharge from the outlet thereof with resultant optimum operation, even at relatively high pulse frequencies in the order of 300 to 400 Hz, and which will permit tuning of the unit depending upon the characteristics of the hydraulic system in which it is installed for maximum dampening action with minimum pressure drop.
Another object of the invention is to provide a unit of the above type in which the central tube through which the liquid flows is free to expand axially, thereby preventing cracking thereof with variations in temperature and in which dependable sealing of the inlet and outlet ends of the unit is provided regardless of expansion and contraction of the unit.
According to the invention, these objects are accomplished by the arrangement and combination of elements hereinafter described and more particularly recited in the claims.
In the accompanying drawings in which are shown one of various possible embodiments of the several features of the invention,
FIG.-I is a longitudinal sectional view of a pulse damper unit according to the invention;
FIG. 2 is a view similar to FIG. 1 on an enlarged scale and with parts broken away, and
FIG. 3 is a perspective view of a washer forming part of a permeable wall.
Referring now to the drawings, the pulse damper unit comprises a rigid container having a cylindrical body portion 11 and hemispherical ends 10a and 10b having axially aligned ports 11a, 11b respectively.
The container 10 may be of any suitable material capable of withstanding the pressures to which it is subjected in use and preferably is of steel.
Positioned in each of the ports Ila, 11b is a nipple or fitting in the form of a sleeve 12a, 12b, each internally threaded as at 13 to receive correspondingly threaded pipes or conduits (not shown), by means of which the pulse damper unit is connected into the hydraulic installation.
In order to mount each of the nipples 12a, 12b in the associated port 11a, 11b, as illustratively shown, a deformable locking ring 14 is associated with each nipple. The locking ring desirably comprises a plurality of annular rigid segments 140 at least two in number with adjacent ends in juxtaposition. The segments have a continuous ring 15 of resilient material such as rubber, bonded to the periphery 14b and to the inner surface 14c thereof, the outer diameter of the ring 15 being greater than that of the segments 14a.
As clearly shown, the outer surface of each of the segments has an arcuate projection defining an annular hub 14d when the segments are juxtaposed.
To mount the nipple 12a, the associated ring 14 is bent so that it may be passed into the container through the port 11a and then the ring is permitted to re-expand to assume its normal shape. The nipple 12a, which had been previously inserted into the container through port 11a, is inserted through ring 14 until flange 18 of the nipple 12a abuts against the inner periphery 19 of segments 14a.
With the nipple 12a pulled outwardly, the outer surface l4e thereof will abut against the inner surface 16 of the container adjacent port 110. In addition, the outer surface 15a of the resilient ring 15 will be in juxtaposition with the inner surface of the container.
By reason of the hub 14d, the nipple will remain centered in port 11a.
Encompassing the nipple 12a is a gasket 26, and an O-ring 23 which are positioned in the clearance S defined between the wall of port 11a and the outer surface 17 of nipple 12a.
Associated with the nipple 12a is a retainig ring 22 of diameter greater than that of port 11a and having a central opening of diameter just slightly larger than that of nipple 12a so that it may readily encompass the latter. The ring 22 is of reduced outer diameter at its inner end defining an annular shoulder 28' and an annular hub 25, which extends into the clearance S, said hub 25 having a beveled inner surface 25a. The shoulder-28' has an annular groove 27 in which is positioned an O- ring 24, the shoulder 28' and O-ring 24 abutting against a plane surface 28 encompassing port Ila.
The nipple or fitting 12a is securely locked in the port 11a by a nut 20, screwed on the externally threaded end 21 of fitting 120. As a result, when the nut 20 is tightened, the fitting 12a will be pulled outwardly, such movement being limited by the abutment of flange 18 against segments 14a and of segments 14a against the surface 16 of the container. Tightening of nut 20 will also force locking ring 22 inwardly, so that O-ring 24 will press against plane surface 28 to form a seal. In addition, the O-ring 23 will also form a seal.
Thus, regardless of the conditions of expansion of the container and the other rigid elements, due to the beveled surface 25a against which O-ring 23 abuts, an axial seal is assured and due to O-ring 24, which abuts against plane surface 28, a radial seal is assured.
Positioned in the container is a flexible spearator 30 in the form of an elongated bladder having hemispherical ends. The bladder is of resilient deformable material such as rubber which may be natural or synthetic.
The. bladder defines an inner chamber 31 and an outer chamber 32 each with variable volume.
The cylindrical portion 11 of the container has a transverse port 10' extending centrally therethrough and internally threaded as shown, in order that it may receive a fitting 33 to enable the chamber 32 to be charged with fluid under pressure, and more particularly, with gas under pressure in the example shown, it being understood that it is also possible to have the fitting 33 a liquid fitting, for liquid under pressure.
The bladder 30 has a pair of axially aligned ports or openings 34a and 34b in the hemispherical ends thereof. The openings 34a and 34b are associated respectively with the fitting 12a and 12b.
The bladder 30 is illustratively made in two sections 300 and 30b each having the associated opening 340 and 34b. The bladder 30 is preferably assembled by gluing or bonding the adjacent bevelled edges thereof as at 30c. To mount the bladder, there is positioned in opening 340 a rigid ring 35a, which is substantially L- shaped in cross section. A similar ring 35b is mounted in the opening 34b. Preferably, each of the sections 30a and 30b is formed with the rings 35a, 35b molded integrally therewith.
Each of the rings 35a and 35b encompasses a smooth cylindrical outer surface 36 of a sleeve 37a, 37b, each of said sleeves having an externally threaded portion 38 on the outer side of the portion 36, which screws into the threaded end of the associated fitting 12a, 12b. Furthermore, each of the sleeves 37a, 37b has on the inner side of the smooth cylindrical surface 36, an enlarged portion defining an annular shoulder 39 against which the associated ring 35a, 35b may abut. The enlarged portion has a conical outer surface 41 of greater diameter at its outer end as at 40', an annular groove 40 being provided between said end 40 and the shoulder 39 to provide clearance.
The rings 35a, 35b which encompass the cylindrical portion 36 are retained on sleeves 37a and 37b in abutment against shoulder 39 by spring clips 42.
It is to be noted that when so assembled the bladder material at the opening 34a, 34b is clamped or pinched between the ring 35a, 35b and the floor of the annular groove 40.
Furthermore, when the sleeves 37a, 37b are screwed into the associated sleeve 12a, 12b the bladder material adjacent the opening 34a, 34b is clamped or pinched between the ring 35a, 35b and the flange 18 of nipples 12a, 12b. As a result, an excellent seal is provided.
Extending axially in the container 10 is an elongated tube 50 having a longitudinal bore or passageway 51, the tube 51 having a plurality of perforations 53.
The tube 50 is of enlarged diameter at one end as at 55a, said enlarged diameter end being externally threaded as at 56 so that it may be screwed into the threaded portion 13 of fitting 12a, by means of a wrench engaging openings 60 in end 55a. The enlarged diameter end portion 55a defines an annular shoulder 55 which abuts against the outer end of sleeve 37a. The tube 50 has a reduced diameter portion 55" defining a second annular shoulder 50" which is inwardly spaced from annular shoulder 55. The region between said two annular shoulders 50, 50" defines a smooth cylindrical surface 57 extending through the bore of sleeve 37a.
The end 55b of tube is encompassed by a removable sleeve 62 which is secured in fixed position at end b by a set screw 63. The outer surface 57 of sleeve 62 defines a smooth cylindrical portion which extends through the bore of sleeve 37b so that it is slidable therein.
Encompassing the reduced diameter portion 50" of tube 50 is a stack of washers 54. The washers are mounted on the tube before the latter is positioned in the container. This is accomplished by sliding the washers on the reduced diameter 50" of the tube so that they abut against shoulder 50" and when sufficient washers have been mounted on the tube the sleeve 62 is positioned on the end 55b and moved axially to clamp the washers together, and the sleeve 62 is then locked in place by the set screw 63. The washers are of the type having a central opening 70 with a plurality of radially extending grooves 71 extending from the central opening to the periphery 72 of the washer. As illustratively shown, the grooves 71 are provided in only one surface of each washer, but of course both surfaces of the washers can be grooved.
Thus, when the washers are assembled as above described, to form a stack, the grooves will define a plurality of substantially radially extending passageways from the central opening of the washer to the exterior.
It will be thus noted that by reason of the perforations 53 in the tube 50 and the grooves 71 in the washer, the
central bore or passageway 51 of the tube will communicate with the inner chamber 31 defined by the bladder.
Positioned in the bore or passageway 51 of tube 50 is a baffle or deflection member in the form of a plug having opposed conical ends, which interrupts continuous flow of liquid through the tube. The deflection member 60 has a transverse bore therethrough, through which a removable pin 61 extends, the latter engaging diametrically opposed perforations 53 in the tube. Consequently the baffle member can be located as desired, either in the center of the tube 50 or at each side of the center in order to create different losses of head on the inlet or outlet side of the unit to avoid harmonies developing and resonance in the installation.
More particularly, by proper location of the deflection or baffle member 60', the damper can be tuned so that it is capable of absorbing pulsation of high frequencies, for example, in the order of 300 to 400 Hz per second.
In operation, the pulse damper unit is connected in the hydraulic system, for example, by having the unit inserted in a hydraulic line which is connected to the fittings 12a and 12b so that the hydraulic liquid flowing into inlet fitting 12a will discharge through outlet fitting 12b.
It is important for efficient pulse damping operation that substantially all of the fluid entering inlet fitting 12a be subjected to the damping action of the unit before the fluid is discharged through outlet fitting 12b.
The unit is precharged with gas under pressure through fitting 33 which will cause the chamber 32 to be charged with such gas so that the deformable bladder 30 will be moved inwardly against the outer periphery of the stack of washers 54.
Due to the fact that the passageways defined by the grooves 71 in the washers 54 are of relatively small diameter, the bladder will not extrude into such passageway. However, by reason of the multiplicity of passageways defined by the large number of grooves, and by reason of the relatively large diameter of the perforations 53 in tube 50, rapid flow of liquid will be permitted between the passageway 51 and the chamber 31 for efficient operation. 4
Depending upon the frequency of the pump used in the system, the baffle member 60' is positioned in an optimum location so that pressure drops will be minimized.
When the fluid is forced through inlet fitting 12a it will pass into the passageway 51 on the right side of the baffle member 60 and by reason of the latter the fluid will then pass through the perforations 53 and grooves 71 into chamber 31 to cause the fluid to be moved outwardly thereby expanding bladder 30 and compressing the gas in chamber 32. Thereupon, the liquid forced into the chamber 31 will then flow through the grooves 71 of washers 54 and through the perforations 53 on the left hand side of baffle member 60 into the portion of passageway 51 on the left side of the baffle member 60' to be discharged through outlet fitting 12b.
As a result of the foregoing, the pulses in the fluid will be substantially absorbed by the compression of the gas in chamber 32, so that the liquid discharged from port 12b will have pulses of a minimum of amplitude.
By reason of the adjustable nature of baffle member 60, it is possible by adjusting the position of such member, depending upon characteristics of each installation, to optimise the dampening effect with avoidance of resonance phenomena which could rapidly build up the amplitude of the pulses.
It is to be noted that in systems of the above type, due to variations in ambient temperature and in the temperature of the hydraulic liquid utilized, expansion and contraction of the various components utilized in the unit may occur. Such expansion and contraction is most pronounced in tube 50 through which the hydraulic liquid flows.
By reason of the sliding connection of the end 55b of the tube 50, it is free to move axially so that breakage of the tube 50, which would otherwise occur if it was rigidly connected at both ends, is precluded.
Furthermore, by reason of the seals provided by 0- rings 23, 24, leakage from the unit even with expansion and contraction thereof is precluded.
Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:
l. A pulse damper unit for a hydraulic system, comprising a rigid container having two axially aligned ports, an inlet fitting and an outlet fitting mounted respectively in said ports for connection of the unit into the hydraulic system, a tube in said container extending between said ports and interconnecting said fittings, said tube having a permeable wall, a deformable bladder in said container encompassing said tube and having two axially aligned ports associated respectively with said fittings, said bladder defining an inner and outer chamber in said container, means for charging said outer chamber with fluid under pressure, and a baffle positioned in said tube between said inlet and outlet fittings, whereby all of the hydraulic fluid entering said inlet fitting will flow through said permeable wall of said tube into said inner chamber before being discharged from said outlet fitting.
2. The combination set forth in claim 1 in which said baffle is axially movable in said tube and means are provided to retain said baffle in desired position.
3. The combination set forth in claim 1 in which said tube has a plurality of perforations therethrough along the length thereof, said baffle is a plug of diameter substantially the same as the inner diameter of said tube, said plug having a diametrical bore therethrough and a pin extends through said bore and through a pair of diametrically aligned perforations in said tube.
4. The combination set forth in claim 1 in which said tube has a plurality of perforations therethrough along the length thereof, and a stack of juxtaposed washers encompass said tube, each of said washers having a plurality of grooves in at least one surface thereof radiating from the axis thereof to the outer periphery, said grooves defining passageways.
5. The combination set forth in claim 1 in which one end of said tube is rigidly connected to one of said fittings and the other end of said tube is slidably mounted with respect to the other of said fittings.
6. The combination set forth in claim 1 in which each of said fittings is a hollow sleeve, a ring member is secured in each of the ports of said bladder, and a retainer sleeve releasably mounted in each of said fitting sleeves, clamps said ring members against said fitting sleeves.
7. The combination set forth in claim 1 in which each of said fittings is an internally threaded sleeve, said tube having an externally threaded portion at one end coacting with the threads of said fitting for secure connection thereto, the other end of said tube extending coaxially through said other fitting and being slidably mounted with respect thereto.
8. The combination set forth in claim 1 in which each of said fittings is a sleeve extending through an associated container port, means releasably locking said fittings in each of said container ports, an O-ring encompassing said fitting and positioned between said fitting and the wall of the associated port to define an annular seal.
9. The combination set forth in claim 1 in which each of said fittings is a sleeve extending through an associated container port, each of said sleeves having a radially extending flange at its inner end of outer diameter less than the diameter of the associated container port, a deformable locking ring encompassing each of said sleeves and interposed between the annular flange and periphery of the associated container port, said locking ring having an annular hub extending between the wall of the associated container port and the associated sleeve, a retainer ring encompassing each of said sleeves externally of said container port, said retainer ring having a reduced diameter portion defining an annular shoulder and an annular hub, said hub extending between the wall of the associated container port and the associated sleeve, the outer end of each sleeve being externally threaded and a nut screwed on said .threaded end to lock said sleeve, said deformable ring and said retainer ring in fixed position with respect to the associated port.
10. The combination set forth in claim 9 in which an O-ring is positioned in said space, between the hub of said deformable locking ring and the hub of said retainer ring, said annular shoulder of said retainer ring having an annular groove and an O-ring positioned in said annular groove to engage the outer surface of said container coaxially with said port.
11. The combination set forth in claim 10 in which said hub of said retainer ring is bevelled.